Hey Gizfreak!
I am beginning to believe the LED is slowly becoming the future for grow lamps. They are by far more efficient then usual MIH/HPS bulbs and can last up to 5 times longer!
Sadly many of the companies selling LED lamps are wildly misconstruing their customers when it comes to total output
(as in saying a light puts out ~300 watts when in reality it only pulls 160-180 from the wall) The reason for this is simple, they are using 3w chips but only running them at about 50-60%.
Be careful when buying! A few good companies that I have seen are growblu, platinumLED, Black dog (I think). And a few other very straightforward sellers. I am actually looking into building my own panel using COB (Chip-on-Board) LED's from Cree or Bridgelux.
Check out the LED section on RIU, there are a dozen or so genius level guys building kick-ass DIY lights over there. Some of the science/growing over there is simply astonishing
http://www.rollitup.org/f/led-and-other-lighting.124/Oh and P.S. if someone is telling you an LED doesn't put out heat they are trying to sell you something
An LED lamp will usually exhaust its heat upward and away from the canopy but, while they don't require a ventilation system like and HPS bulb would it still requires some attention.